import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:go_router/go_router.dart';
import 'package:lucide_icons/lucide_icons.dart';
import 'package:social_app/core/l10n/l10n.dart';
import '../../../../app/di/injection.dart';
import '../../../../app/router/app_routes.dart';
import '../../../../core/theme/design_tokens.dart';
import '../../../../features/calendar/data/repositories/calendar_repository.dart';
import '../../../../shared/widgets/app_pressable.dart';
import '../../../../shared/widgets/bottom_dock.dart';
import '../../../../shared/state/calendar_state_manager.dart';
import '../../../../app/router/home_return_policy.dart';
import '../calendar_time_utils.dart';
import '../utils/event_color_resolver.dart';
import '../../../../features/calendar/data/models/schedule_item_model.dart';

class CalendarMonthScreen extends StatefulWidget {
  final bool resetToToday;

  const CalendarMonthScreen({super.key, this.resetToToday = false});

  @override
  State<CalendarMonthScreen> createState() => _CalendarMonthScreenState();
}

class _CalendarMonthScreenState extends State<CalendarMonthScreen>
    with WidgetsBindingObserver {
  late final CalendarStateManager _calendarManager;
  late DateTime _currentMonth;
  late DateTime _selectedDate;
  final Map<String, List<ScheduleItemModel>> _eventsByDay = {};

  ColorScheme get _colorScheme => Theme.of(context).colorScheme;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    _calendarManager = sl<CalendarStateManager>();

    if (widget.resetToToday) {
      _calendarManager.resetToToday();
    }

    final savedDate = _calendarManager.selectedDate;
    _selectedDate = savedDate;
    _currentMonth = DateTime(savedDate.year, savedDate.month, 1);
    _loadMonthEvents();
  }

  Future<void> _loadMonthEvents({bool forceRefresh = false}) async {
    final events = await sl<CalendarRepository>().getMonthEvents(
      _currentMonth,
      forceRefresh: forceRefresh,
    );
    if (!mounted) {
      return;
    }
    _eventsByDay.clear();
    for (final event in events.where(
      (e) => e.status != ScheduleStatus.archived,
    )) {
      final key = formatYmd(event.startAt);
      _eventsByDay[key] = [...(_eventsByDay[key] ?? const []), event];
    }
    setState(() {});
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      _loadMonthEvents(forceRefresh: true);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: _colorScheme.surface,
      body: PopScope(
        canPop: false,
        onPopInvokedWithResult: (didPop, result) {
          if (!didPop) {
            returnToHomePreserveState(context, forceGoHome: true);
          }
        },
        child: SafeArea(
          child: Column(
            children: [
              _buildHeader(),
              Expanded(
                child: SingleChildScrollView(
                  child: Padding(
                    padding: const EdgeInsets.only(bottom: 84),
                    child: _buildMonthContent(),
                  ),
                ),
              ),
              _buildBottomDock(),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildHeader() {
    final l10n = context.l10n;
    final today = DateTime.now();
    final isNotToday = !isSameDay(_selectedDate, today);

    return SizedBox(
      height: 76,
      child: Padding(
        padding: const EdgeInsets.only(left: 16, right: 16, top: 14, bottom: 6),
        child: Column(
          children: [
            SizedBox(
              height: 56,
              child: Row(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  AppPressable(
                    borderRadius: BorderRadius.circular(AppRadius.md),
                    onTap: _showMonthPicker,
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        AnimatedSwitcher(
                          duration: const Duration(milliseconds: 160),
                          switchInCurve: Curves.easeOut,
                          switchOutCurve: Curves.easeOut,
                          child: Text(
                            l10n.calendarMonthHeader(_currentMonth.month),
                            key: ValueKey(_currentMonth.month),
                            style: TextStyle(
                              fontSize: 22,
                              fontWeight: FontWeight.w700,
                              color: _colorScheme.onSurface,
                            ),
                          ),
                        ),
                        const SizedBox(width: 6),
                        Icon(
                          LucideIcons.chevronDown,
                          size: 16,
                          color: _colorScheme.onSurface,
                        ),
                      ],
                    ),
                  ),
                  const Spacer(),
                  if (isNotToday)
                    AppPressable(
                      borderRadius: BorderRadius.circular(AppRadius.xl),
                      onTap: _goToToday,
                      child: Container(
                        height: 36,
                        padding: const EdgeInsets.symmetric(horizontal: 12),
                        decoration: BoxDecoration(
                          color: _colorScheme.surfaceContainerLow,
                          borderRadius: BorderRadius.circular(AppRadius.xl),
                          border: Border.all(
                            color: _colorScheme.outlineVariant,
                          ),
                        ),
                        child: Center(
                          child: Text(
                            l10n.calendarMonthToday,
                            style: TextStyle(
                              fontSize: 14,
                              fontWeight: FontWeight.w600,
                              color: _colorScheme.onSurface,
                            ),
                          ),
                        ),
                      ),
                    ),
                  if (isNotToday) const SizedBox(width: 8),
                  AppPressable(
                    borderRadius: BorderRadius.circular(AppRadius.full),
                    onTap: () async {
                      final changed = await context.push<bool>(
                        AppRoutes.calendarEventCreate,
                      );
                      if (changed == true) {
                        await _loadMonthEvents(forceRefresh: true);
                      }
                    },
                    child: Container(
                      width: 36,
                      height: 36,
                      decoration: BoxDecoration(
                        color: _colorScheme.primary,
                        borderRadius: BorderRadius.circular(AppRadius.full),
                      ),
                      child: Icon(
                        LucideIcons.plus,
                        size: 20,
                        color: _colorScheme.onPrimary,
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  void _goToToday() {
    final today = DateTime.now();
    final targetMonth = DateTime(today.year, today.month, 1);
    setState(() {
      _selectedDate = today;
      if (_currentMonth.year != targetMonth.year ||
          _currentMonth.month != targetMonth.month) {
        _currentMonth = targetMonth;
      }
    });
    _calendarManager.setSelectedDate(today);
    _loadMonthEvents(forceRefresh: true);
  }

  Widget _buildMonthContent() {
    return Column(
      children: [
        _buildWeekdayHeader(),
        Container(height: 1, color: _colorScheme.outlineVariant),
        ..._buildWeeks(),
      ],
    );
  }

  Widget _buildWeekdayHeader() {
    final l10n = context.l10n;
    final List<String> weekdays = [
      l10n.calendarMonthWeekdaySunShort,
      l10n.calendarMonthWeekdayMonShort,
      l10n.calendarMonthWeekdayTueShort,
      l10n.calendarMonthWeekdayWedShort,
      l10n.calendarMonthWeekdayThuShort,
      l10n.calendarMonthWeekdayFriShort,
      l10n.calendarMonthWeekdaySatShort,
    ];
    return SizedBox(
      height: 40,
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 16),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: weekdays
              .map(
                (day) => SizedBox(
                  width: 36,
                  child: Center(
                    child: Text(
                      day,
                      style: TextStyle(
                        fontSize: 11,
                        fontWeight: FontWeight.w600,
                        color: _colorScheme.onSurfaceVariant,
                      ),
                    ),
                  ),
                ),
              )
              .toList(),
        ),
      ),
    );
  }

  List<Widget> _buildWeeks() {
    final firstDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month,
      1,
    );
    final lastDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month + 1,
      0,
    );
    final startWeekday = firstDayOfMonth.weekday % 7;

    final daysInMonth = lastDayOfMonth.day;
    final totalCells = ((daysInMonth + startWeekday) / 7).ceil() * 7;

    final weeks = <Widget>[];
    for (var weekStart = 0; weekStart < totalCells; weekStart += 7) {
      weeks.add(_buildWeekRow(weekStart, startWeekday, daysInMonth));
      if (weekStart + 7 < totalCells) {
        weeks.add(Container(height: 1, color: _colorScheme.outlineVariant));
      }
    }

    return weeks;
  }

  Widget _buildWeekRow(int weekStart, int startWeekday, int daysInMonth) {
    return Padding(
      padding: const EdgeInsets.only(left: 16, right: 16, top: 14, bottom: 0),
      child: Column(
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: List.generate(7, (index) {
              final dayIndex = weekStart + index - startWeekday + 1;
              if (dayIndex < 1 || dayIndex > daysInMonth) {
                return SizedBox(width: 36, height: 36);
              }

              final date = DateTime(
                _currentMonth.year,
                _currentMonth.month,
                dayIndex,
              );
              final isSelected = isSameDay(_selectedDate, date);

              return AppPressable(
                borderRadius: BorderRadius.circular(AppRadius.full),
                onTap: () {
                  setState(() {
                    _selectedDate = date;
                  });
                  _calendarManager.setSelectedDate(date);
                  _calendarManager.setViewType(CalendarViewType.month);
                  context.push(
                    '${AppRoutes.calendarDayWeek}?date=${formatYmd(date)}',
                  );
                },
                child: Container(
                  width: 36,
                  height: 36,
                  decoration: BoxDecoration(
                    color: isSelected
                        ? _colorScheme.primaryContainer
                        : _colorScheme.surface.withValues(alpha: 0),
                    borderRadius: BorderRadius.circular(AppRadius.full),
                  ),
                  child: Center(
                    child: Text(
                      '$dayIndex',
                      style: TextStyle(
                        fontSize: 15,
                        fontWeight: isSelected
                            ? FontWeight.w600
                            : FontWeight.normal,
                        color: isSelected
                            ? _colorScheme.primary
                            : _colorScheme.onSurface,
                      ),
                    ),
                  ),
                ),
              );
            }),
          ),
          const SizedBox(height: 10),
          _buildWeekEvents(weekStart, startWeekday, daysInMonth),
        ],
      ),
    );
  }

  Widget _buildWeekEvents(int weekStart, int startWeekday, int daysInMonth) {
    final firstDayOfMonth = DateTime(
      _currentMonth.year,
      _currentMonth.month,
      1,
    );
    final weekFirstDate = firstDayOfMonth.add(
      Duration(days: weekStart - startWeekday),
    );

    return SizedBox(
      height: 70,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: List.generate(7, (index) {
          final dayIndex = weekStart + index - startWeekday + 1;
          if (dayIndex < 1 || dayIndex > daysInMonth) {
            return const SizedBox(width: 38, height: 1);
          }

          final date = weekFirstDate.add(Duration(days: index));
          final events = _eventsByDay[formatYmd(date)] ?? const [];
          final displayEvents = events.take(2).toList();
          final remainingCount = events.length - 2;

          return SizedBox(
            width: 38,
            height: 70,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                ...displayEvents.map((event) {
                  final color = resolveEventColor(
                    status: event.status,
                    colorHex: event.metadata?.color,
                  );
                  return AppPressable(
                    borderRadius: BorderRadius.circular(AppRadius.sm),
                    onTap: () async {
                      _calendarManager.setSelectedDate(date);
                      final changed = await context.push<bool>(
                        '/calendar/events/${event.id}',
                      );
                      if (changed == true) {
                        await _loadMonthEvents(forceRefresh: true);
                      }
                    },
                    child: Container(
                      margin: const EdgeInsets.only(bottom: 2),
                      padding: const EdgeInsets.symmetric(
                        horizontal: 4,
                        vertical: 2,
                      ),
                      decoration: BoxDecoration(
                        color: color.withValues(alpha: 0.2),
                        borderRadius: BorderRadius.circular(4),
                      ),
                      child: Text(
                        event.title,
                        style: TextStyle(
                          fontSize: 9,
                          color: color,
                          fontWeight: FontWeight.w500,
                        ),
                        maxLines: 1,
                        overflow: TextOverflow.ellipsis,
                      ),
                    ),
                  );
                }),
                if (remainingCount > 0)
                  AppPressable(
                    borderRadius: BorderRadius.circular(AppRadius.sm),
                    onTap: () {
                      _calendarManager.setSelectedDate(date);
                      _calendarManager.setViewType(CalendarViewType.day);
                      context.push(
                        '${AppRoutes.calendarDayWeek}?date=${formatYmd(date)}',
                      );
                    },
                    child: Text(
                      '+$remainingCount',
                      style: TextStyle(
                        fontSize: 9,
                        color: _colorScheme.onSurfaceVariant,
                        fontWeight: FontWeight.w500,
                      ),
                    ),
                  ),
              ],
            ),
          );
        }),
      ),
    );
  }

  void _showMonthPicker() {
    final l10n = context.l10n;
    var selectedYear = _currentMonth.year;
    var selectedMonth = _currentMonth.month;

    showModalBottomSheet(
      context: context,
      backgroundColor: _colorScheme.surface,
      builder: (context) {
        return StatefulBuilder(
          builder: (context, setSheetState) {
            return SizedBox(
              height: 300,
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
                    crossAxisAlignment: CrossAxisAlignment.center,
                    children: [
                      TextButton(
                        onPressed: () => Navigator.pop(context),
                        child: Text(l10n.commonCancel),
                      ),
                      TextButton(
                        onPressed: () {
                          Navigator.pop(context);
                          setState(() {
                            _currentMonth = DateTime(
                              selectedYear,
                              selectedMonth,
                              1,
                            );
                            _selectedDate = DateTime(
                              selectedYear,
                              selectedMonth,
                              1,
                            );
                          });
                          _calendarManager.setSelectedDate(_selectedDate);
                          _loadMonthEvents();
                        },
                        child: Text(l10n.commonConfirm),
                      ),
                    ],
                  ),
                  Expanded(
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        Expanded(
                          child: CupertinoPicker(
                            itemExtent: 40,
                            scrollController: FixedExtentScrollController(
                              initialItem: _currentMonth.year - 2020,
                            ),
                            onSelectedItemChanged: (index) {
                              setSheetState(() {
                                selectedYear = 2020 + index;
                              });
                            },
                            children: List.generate(20, (index) {
                              return Center(
                                child: Text(
                                  l10n.calendarMonthYearLabel(2020 + index),
                                ),
                              );
                            }),
                          ),
                        ),
                        Expanded(
                          child: CupertinoPicker(
                            itemExtent: 40,
                            scrollController: FixedExtentScrollController(
                              initialItem: _currentMonth.month - 1,
                            ),
                            onSelectedItemChanged: (index) {
                              setSheetState(() {
                                selectedMonth = index + 1;
                              });
                            },
                            children: List.generate(12, (index) {
                              return Center(
                                child: Text(
                                  l10n.calendarMonthHeader(index + 1),
                                ),
                              );
                            }),
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            );
          },
        );
      },
    );
  }

  Widget _buildBottomDock() {
    return BottomDock(
      activeTab: DockTab.calendar,
      onTodoTap: () {
        _calendarManager.setViewType(CalendarViewType.month);
        context.push(AppRoutes.todoList);
      },
      onCalendarTap: () {},
      onHomeTap: () => returnToHomePreserveState(context, forceGoHome: true),
    );
  }
}